In March, Karachi-based United Bank Ltd. plunged 7 percent on rumors its chief executive officer was arrested. The company denied it, the stock bounced, though not all the way back.

A month earlier, shares of Hascol Petroleum Ltd. dropped the most since 2015 as messages circulated on WhatsApp that the company had been ordered to pay $60 million after losing an arbitration case against MENA Energy. The fine is “a figment of someone’s imagination,” Hascol said in a March 1 filing.

Social media chatter aimed at stocks has become a fact of life in Pakistan, prompting authorities to crack down. The nation’s Securities and Exchange Commission has closed seven groups of tippers that gathered on Facebook, and is probing 25 others, Chairman Zafar Hijazi said in an interview. At least 84 companies have been asked to explain abnormal price movements since July, more than double in the previous 13 months, he said. Most have no idea what drove the shares and some blame it on rumors, Hijazi said.

“The market over here is not very advanced,” Imtiaz ul Haq, an assistant professor of economics at the Lahore University of Management Sciences, said in an interview. “A lot of investors say to me: you’re a PhD, give us some tips. That’s what the market seems to be working on. Tips.”

The regulator is trying to halt the spread of misinformation in a market slated to be added to MSCI Inc.’s emerging-market gauges this month. It wants to help investors dodge fraudsters making false claims about stocks amid a boom that made Pakistani stocks Asia’s biggest gainers in 2016. Neighbor India, with 130 million Facebook users, is also working on rules to curb the spread of unsolicited investment advice through digital platforms.

The efforts will take time to pay off in frontier markets like Pakistan where local investors drive as much as 90 percent of the volume, according to Tundra Fonder AB, which has about $150 million in Pakistani stocks. The KSE100 Index has risen about 40 percent in the past 12 months, the seventh-biggest gainer among 96 primary equity gauges. The index gained 0.3 percent at 9:55 a.m. local time, halting four days of declines.

“Most people are skeptical of things they see on social media, but I don’t know why they believe in it when it comes to Pakistan,” Mattias Martinsson, the Stockholm-based chief investment officer at Tundra, said by phone. “Social media is tough to control. The only thing to do is to educate investors. This is the hard way to learn, unfortunately.”

Manipulators have also used Pakistan’s growing economic ties with China as a bait to lure investors.

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Nazir Cotton Mills Ltd.’s shares more than tripled from end of October through the middle of December after a WhatsApp message on the company being bought by Chinese investors did the rounds. Nazir, whose factory has been shut for a decade, in a filing in November denied the rumor and asked investors to be careful before buying its shares. The stock has since returned to earth, slumping 64 percent in 2017.

“We have referred this matter to the Federal Investigation Agency and I was told that it has registered first information reports” against the fraudsters, the SEC’s Hijazi said.

The regulator received 20 cases of price rigging from the Pakistan Stock Exchange in 2016, the highest in six years. Creating awareness and probing unusual swings is the most that an exchange can do, Deputy Managing Director Haroon Askari said in Karachi.

Some investors don’t mind trading on social media tips as long as they make money.

“You can take part in a rally even if it is fueled by fake news,” said Ali, a manager at one of Karachi’s ports. “This sometimes helps me judge market trends.”